Messages in this thread | | | From | Linus Torvalds <> | Date | Thu, 21 Jul 2022 11:06:42 -0700 | Subject | Re: [patch 00/38] x86/retbleed: Call depth tracking mitigation |
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On Thu, Jul 21, 2022 at 10:56 AM Peter Zijlstra <peterz@infradead.org> wrote: > > this seems to work, let me go hack the kernel..
Am I missing something?
Isn't this generating
movl $~IMM,%r10d negl %r10d cmpl %r10d,-4(%calldest)
for the sequence?
That seems bogus for two reasons:
(a) 'neg' is not the opposite of '~'. Did you mean 'notl' or did you mean '-'?
Or am I missing something entirely?
(b) since you have that r10 use anyway, why can't you just generate the simpler
movl $-IMM,%r10d addl -4(%calldest),%r10d
instead? You only need ZF anyway.
Maybe you need to add some "r10 is clobbered" thing, I don't know.
But again: I don't know llvm, so the above is basically me just doing the "pattern matching monkey" thing.
Linus
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